As one of techniques for reducing power consumption or improving performance (operation characteristic) of a transistor, a high-mobility channel material that increases mobility of carriers has been examined. At a channel improved in carrier transport property, a drain current in an ON state can be increased. Therefore, it is possible to sufficiently obtain an ON-state current and also possible to reduce a power supply voltage. This combination brings about higher performance of a MOSFET (metal oxide semiconductor field-effect transistor) with low power consumption.
Compounds from group III-V, compounds from group IV, Ge (germanium), and graphene containing only C (carbon) have been expected to be used as high-mobility channel materials. At present, in the case of forming a channel of the compounds from group III-V, there is a problem that a technique of improving crystallinity of the channel and readily controlling and growing a shape of the channel has not been established. Therefore, the compounds, particularly SiGe and Ge, from group IV easy to employ as compared with the compounds from group III-V have been actively examined.
A channel using a high-mobility material can be formed by polishing a polishing object including a group IV compound channel, and/or a Ge channel (herein after, sometimes referred to as “Ge material portion”) and a portion that contains a silicon material (herein after, sometimes referred to as “silicon material portion”). In this case, along with polishing of the Ge material portion at a high polishing rate, it is required not to form a stepped portion caused by etching of a polished surface of the polishing object. However, polishing compositions, which have been conventionally used for polishing a Ge substrate, as described in, for example, JP 2010-130009A or JP 2010-519740W (US2011/0117740 (A1)) have been developed for Ge substrate. Therefore, in the case of using such compositions for polishing a polishing object including a Ge material portion and other portions, the Ge material portion may be excessively polished and etched. Thus, it is difficult to prevent formation of a stepped portion caused by etching of a polished surface of the polishing object.